A magnetic disk apparatus is a storage device which allows an actuator to position the magnetic head to a desired track on a rotating magnetic disk to thereby read data from that track or write data on that track by the magnetic head.
This magnetic disk apparatus is widely used as an external storage device. To meet the recent demand of downsizing of computer systems, there is a demand for a small magnetic disk apparatus with a large capacity. The size of magnetic disks tends toward 3.5 inches or 1.8 inches from 5.25 inches.
The size reduction of the magnetic disk apparatus and the large capacity require high-density recording. When high-density recording is performed, however, the magnetic force lines of a magnetic disk medium become short, so that it is preferable that planar recording or perpendicular recording be performed with the floating amount of the head set as small as or below the order of microns, or that perpendicular recording be performed with the head brought in contact with the magnetic disk.
In the case where the floating amount of the head is small or the head is brought in contact with the disk, if the head is heavy, the trackability to undulations or protrusions of the magnetic disk medium decreases on the order of microns.
If the load of the head is increased to improve this trackability, on the other hand, the force of contact with the protrusions of the magnetic disk medium increases, increasing the risk of head crash and medium crash.
Therefore, as the mass of the head decreases and the load of the head decreases, the trackability to a magnetic disk medium increases, so that high-density recording becomes possible with the reduced floating amount of the head or the head brought in contact with the medium.
FIGS. 1(A), 1(B) and 1(C) are diagrams showing the structure of a conventional magnetic head, and FIG. 2 is a diagram illustrating a fabrication process for the head.
As an example of a contact type perpendicular recording head, a flexible magnetic head 9 as shown in FIGS. 1(A-C) has been proposed (see Japanese Unexamined Patent Publication No. 178017/1991, for example).
In this head 9, as shown in FIG. 1(B), a main pole (main magnetic pole) 90 is formed vertically in a dielectric flexure body 96 of aluminum oxide or the like, a yoke 91 connected to this pole is formed horizontally, a back stud 93 connected to this yoke is formed vertically, and a return yoke 94 connected to this stud is formed horizontally, those components constitute a reluctance path. This path ends at a high reluctance gap 95 between the main pole 90 and the return yoke 94.
A spiral coil is inductively coupled to the yoke 91, both ends of the coil 92 connected via lead conductors 97 to bonding pads 98.
This head is called a probe type head, which is fabricated with thin-film forming technology and can be made very small. For instance, as shown in FIG. 1(A), the head 9 has a width D of 0.5 mm, a thickness B of 0.05 mm, a length A of 12.5 mm, and mass of 100 micrograms.
By attaching such a head 9 to an arm, low mass and low load of the head become possible, thus ensuring high-density perpendicular recording in tracking with the undulation of the magnetic disk medium.
This head 9 is formed as an integrated unit using thin film and photolithography technologies. As shown in FIG. 2, many heads are formed on a polished wafer 9-1 of barium titanate or the like in the order of microns through tens of steps by sputtering, vapor deposition, plating, chemical deposition, ion beam deposition and etching, etc., and those heads are scribed to be individual heads.
But, the prior art has the following problems.
(1) The greater the number of heads formed on the wafer 9-1 is, the lower the cost becomes. However, since the lead conductor portion is formed integrally in the prior art, the number of heads formable on the wafer 9-1 is limited; for example, only about 270 heads can be formed on a 3-inch wafer. This significantly increases the cost of the heads.
(2) If the heads are large, the number of defects in the heads cut out of the wafer 9-1 increases; for example, even if the lead conductor portion alone is defective, the whole head becomes defective. This further increases the cost of the heads.